Method and installation for reducing orefines in a multi-stage suspension gas stream using a cyclone separator

ABSTRACT

The invention relates to the reduction of fine ores, whereby in a multi-stage gas suspension preheater the fine ores are preheated, calcined and then reduced in at least one lowest heat exchanger stage with the addition of a reducing agent in a delivered hot gas stream. The principal part of the reducing heat treatment of the fine ores is carried out in a reactor loop constructed in the lowest heat exchanger stage of the gas suspension preheater. The reactor loop has an uptake conduit section and a curved section adjoining the uptake conduit section and with which the reactor loop opens into at least one precipitating cyclone which is disposed downstream and for this purpose a hot reducing gas is introduced into the rising hot gas stream.

The invention relates to a method and to apparatus for the reduction offine ores.

It is generally known that fine ores, e.g. iron, nickel, chromium andmanganese ores, can be dried, preheated, calcined and partially reducedor pre-reduced using a gas suspension preheater or reactor. For morethorough reduction of these pre-reduced fine ores a rotary kiln or anelectric kiln can be connected downstream, and the pre-reduced fine orescan be delivered to it—depending upon the equipment of the electrickiln—in the hot-briquetted state or directly.

An example for the reduction of fine ores is described for instance inDE-A-28 52 964. According to this publication, the ores which arepreheated, calcined and pre-reduced in a gas suspension preheater arefirst of all hot-briquetted and then finally reduced in an electric kilnfrom which hot exhaust gases are led via a kiln exhaust gas conduit totwo cyclones which form the lowest cyclone stage of the gas suspensionpreheater. An additional combustion chamber and—between this additionalcombustion chamber and the lowest cyclone stage—a feed conduit for finecoal is connected to this kiln exhaust gas conduit. With the aid of theadditional combustion chamber, the exhaust gases coming from theelectric kiln can be further heated if required, whilst the fine coalintroduced thereafter—when viewed in the gas flow direction—serves assolid reducing agent for the preheated and calcined fine ores.

Although this known construction should create an economical and uniformreduction not only of fine ores but also of lump ores, it has been shownin practice that this object could not be fulfilled at least to theextent which is desired and necessary.

SUMMARY OF THE INVENTION

The object of this invention, therefore, is to make further improvementsto a method apparatus in such a way that the earlier requirements of theaforementioned known construction are met and thus in an extremelyreliable and reproducible manner an economical and uniform reduction inparticular of fine ores is made possible, and moreover good facilitiesfor regulating and influencing the gas suspension preheater should alsobe ensured.

In this method according to the invention, the fine ores to be reducedcan first of all be preheated and calcined in the necessary manner in aheat exchanger stage or in a plurality of heat exchanger stages of thegas suspension preheater or reactor which are disposed one above theother. According to a significant idea of the present invention, theprincipal part, that is to say the principal work of the reducing heattreatment of the preheated and calcined fine ores is carried out in areactor loop specially constructed in the lowest heat exchanger stage ofthe gas suspension preheater (or reactor) with cyclone precipitationdownstream, and for this purpose a hot gaseous reducing agent isintroduced into the rising hot gas stream, so that the necessaryreducing atmosphere can be created and maintained in this reactor loop,and at least partially into the appertaining cyclone separation. In thetests on which the invention is based, it was possible to confirm thatby means of the simple measures, i.e. in particular by the use of a hotgaseous reducing agent and a correspondingly constructed special reactorloop, an extremely reliable and reproducible and especially thoroughreduction of the preheated and calcined fine ores could be achieved, andthis reduction of the fine ores according to the invention can becarried out particularly economically and very uniformly in the lowestheat exchanger stage. Thus since the fine ores can already be reduced toa very great extent in the lowest heat exchanger stage (reducing heatexchanger stage) of the gas suspension preheater, it is frequentlyalready possible for the fine ores coming from the gas suspensionpreheater and reduced in this way to be delivered in a known manner to acorresponding further treatment without the use of a further kiln.

It should be added in this connection that it is known that theresidence time of the fine ores in the gas suspension preheater can bekept relatively short (currently only seconds), even in the case ofintensive heat exchange, so that relatively quick and good facilitiesfor regulating and influencing the gas suspension preheater and thus theoverall heat treatment are available, whereby the intensity or thedegree of reduction of the fine ores can be influenced by theconstruction of the reactor loop, particularly by the length and guidingthereof.

According to an advantageous embodiment of the invention, the hotgaseous reducing agent is produced as a reducing gas in a separatereactor vessel associated with the reactor loop by sub-stoichiometricburning of gaseous, liquid and/or solid fuels and from there isintroduced into the reactor loop. It is particularly advantageous if, inaddition to the fuels, the required combustion air and optionallyadditional mixed gases are introduced into the reactor vessel. Ambientair or air preheated in a heat exchanger can be used as combustion air.Likewise, ambient air, preheated air or also low-oxygen exhaust gas(e.g. from an exhaust gas stack) can be used as mixed gas in orderadditionally to be able to influence the production of reducing gas.

According to a particularly advantageous embodiment of the methodaccording to the invention, at least some of the preheated and calcinedfine ores are introduced into the reactor vessel which simultaneouslyforms a combustion chamber and a reduction vessel, the ores beingexposed in this reactor vessel to a first partial reduction by means ofthe reducing gas produced there and thereafter are introduced togetherwith the reducing gas into the reactor loop for further reduction. Thisoffers various possibilities for subjecting the preheated and calcinedfine ores to an intensive reduction treatment, i.e. apart from thepossibility of using the reactor vessel only as a combustion chamber forproducing the hot reducing gas which is then introduced into the reactorloop into which the preheated and calcined fine ores can also beintroduced together, at least a preferably adjustable fraction of thepreheated and calcined fine ores can be subjected to a first partialreduction in the reactor vessel, whilst the remaining fraction of thepreheated and calcined fine ores is introduced directly into the reactorloop, and moreover of course the entire fraction of preheated andcalcined fine ores can also be first of all partially reduced in thereactor vessel and then largely finally reduced in the reactor loop.

In all these possibilities for reducing heat treatment, the use of thegaseous reducing agent, that is to say above all the hot reducing gasproduced in the reactor vessel, has proved particularly advantageous orsignificant for the desired thorough reduction of the fine ores in thegas suspension preheater or in the lowest heat exchanger stage thereofwith which the reactor vessel is also associated, i.e. this reactorvessel is advantageously a part of the reduction heat exchanger stage inthe gas suspension preheater according to this method according to theinvention.

For the case where the fine ores from the gas suspension preheater whichhave already been largely reduced are to be reduced even further, it isregarded as advantageous for the fine ores coming from the lowest orreducing heat exchanger stage of the gas suspension preheater (and whichare therefore already very largely reduced) to be subjected to a furthercorrective and/or final reduction in a rotary kiln or at least oneelectric kiln. For this case, it may be advantageous in order to supportthe corrective and/or final reduction in the rotary and/or electric kilnto add to or to mix into the fine ores a fraction of fine-grained coaland/or other organic materials (in particular waste materials or thelike which contain heat energy) as additional reducing agent.

Furthermore, in the preceding context in which reducing gas is producedin the rotary or electric kiln from the additional reducing agent, itmay be advantageous for the hot exhaust gases containing the reducinggas from the kiln which is disposed downstream of the gas suspensionpreheater in the ore flow direction to be introduced into the reactorloop of the reduction heat exchanger stage and to be utilized for thereduction in the gas suspension preheater.

For the case where the reduced fine ores are to be further treated forexample in a chemical decomposition process, it is advantageous for thereduced fine ores to be cooled appropriately, for example to atemperature below 120° C., in a cooling zone which is formed inparticular by an indirect rotary cooler.

If according to the method according to the invention, damp startingores are to be reduced, then according to an advantageous furtherembodiment of the invention, these ores can first of all be dried withthe aid of hot exhaust gases from the gas suspension preheater andpreferably in a pneumatic conveyor dryer.

According to a similar embodiment of the invention, it is proposed thatat least partially lumpy and damp starting ores are first of allcomminuted and dried before their reduction, this comminution and dryingpreferably being carried out in a drying and grinding apparatus with hotexhaust gases being delivered from the gas suspension preheater.

In this method according to the invention, it is regarded asadvantageous overall if the reduction work is carried out in the lowestheat exchanger stage of the gas suspension preheater containing thereactor loop at a temperature of approximately 600 to 1000° C.,preferably between approximately 700 and 900° C.

In this case, it may also be advantageous if reducing gas containingcarbon monoxide (CO) and/or (elementary) hydrogen (H₂) or enrichedtherewith is used (e.g. by stoichiometric combustion of an injectedfuel) for the reduction of the preheated and calcined fine ores in thelowest heat exchanger stage.

It should be mentioned in particular in this connection that due to thesub-stoichiometric combustion of fuel (e.g. heavy oil), the reducinggases produced in the reactor vessel contain CO and H₂ gases which areused for the reduction of the fine ores (e.g. of the iron oxidescontained therein). For this reduction, but also in order to meet theheat requirement for the reduction and the radiation losses, more CO andH₂ gas fractions must be contained in the gas stream than aretheoretically necessary for the reduction. These excess gas fractionsare gradually burnt as they pass through the gas suspension preheater orreactor with the addition of more air, so that the most uniformtemperature level possible is maintained, and preferably all combustiblegas constituents should be burnt in the heat exchanger stage above thereduction heat exchanger stage.

BRIEF DESCRIPTION OF THE DRAWINGS

These and further details of the invention will be described in greaterdetail below in connection with an apparatus constructed according tothe invention for the reduction of fine ores. Such an apparatus isillustrated by way of example in the accompanying drawings, in which:

FIG. 1 shows a partially simplified flow diagram of an embodiment of acomplete apparatus according to the invention;

FIG. 2 shows a partial flow diagram for a variant of the apparatus,according to which a rotary kiln and a rotary cooler are disposeddownstream of the gas suspension preheater.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

First of all the apparatus for reduction of fine ores will be describedwith reference to the flow diagram according to FIG. 1. The principalpart of this reduction apparatus which is essential for the actualreduction work is formed above all by a gas suspension reactor or gassuspension preheater I which is preferably constructed—as shown in FIG.1—generally in the form of a multi-stage cyclone heat exchanger which isknown per se and contains a suitable number of cyclone stages disposedone above the other as heat exchanger stages which will be described ingreater detail below. This gas suspension preheater I has—when viewed inthe flow direction of the ores symbolized by solid arrows 1—a drying andgrinding apparatus II disposed upstream of it and an after-treatmentkiln III disposed downstream of it, the latter being formed in thisexample by at least one electric kiln.

With regard to the general construction of the gas suspension preheaterI, it may be stated that this can contain a number of cyclone stagesdisposed one above the other in the usual manner as appropriate for theparticular application, and normally about 3 to 5 cyclone stages willsuffice. According to the embodiment shown in FIG. 1, the gas suspensionpreheater I contains three cyclone stages disposed substantially oneabove the other, namely a first, lowest cyclone stage 2, a second,middle cyclone stage 3 and a third, uppermost cyclone stage 4.

As can be seen by gas conduits represented by double lines and materialconduits represented by single solid lines, the cyclone stages 2, 3, 4of this gas suspension preheater I are in communication with one anothervia the corresponding gas and material conduits in such a way that fineores delivered at the top pass downwards through this gas suspensionpreheater I generally in counter-current flow to rising hot gases whichare delivered at the bottom (broken arrows 5). In this gas suspensionpreheater I, the two upper cyclone stages 3, 4 serve for preheating andprecalcining or calcining the fine ores (arrow 1) delivered at 4 a tothe uppermost cyclone stage 4.

The first, lowest cyclone stage 2 of the gas suspension preheater I isconstructed as a reduction stage, and a hot gas supply in the form of ahot gas conduit 6 coming from the after-treatment kiln/electric kiln IIIis connected to this lowest cyclone stage 2, i.e. the hot kiln exhaustgases (broken arrows 5) from this electric kiln III are utilized atleast for heating or for heat treatment and, if appropriate, partiallyalso for reduction (in so far as reducing gas fractions or CO and H₂gases are contained therein) of the fine ores in the gas suspensionpreheater I. Furthermore, in the region of the lower end of this lowestcyclone stage 2, there is also connected a supply or supply conduit 7through which a reducing agent is introduced into the rising hot gases(arrow 5), as will be described in greater detail below.

In order that the principal reduction work can be done in the first,lowest cyclone stage 2, this cyclone stage 2 is constructed with asufficiently long reactor loop 8 which—as FIG. 1 clearly shows—has arelatively long uptake conduit section 8 a which rises substantiallyvertically in an extension of the hot gas conduit 6 and an upper section8 b which is curved approximately like a swan's neck and adjoins thesection 8 a and with which the reactor loop 8 opens into at least oneprecipitating cyclone 2 a of this cyclone stage 2 which is disposeddownstream. Apart from the hot gas conduit 6, the supply conduit 7 whichhas already been mentioned for the reducing agent is connected in thelower end region of the uptake pipe section 8 a of this reactor loop 8.

As has already been mentioned above, it is regarded as an essential ideato use a gaseous reducing agent and above all a specially preparedreducing gas as reducing agent. This gaseous reducing agent or reducinggas can basically be delivered from any suitable source, so long as itcan be used for sufficient reducing work. In this invention, however, itis particularly preferred if for the production of this reducing gas, areactor vessel 9 is used which is connected via a connecting conduit tothe reactor loop 8, this connecting conduit being advantageously formedin a simple manner by the supply conduit 7 already mentioned above. Alsoconnected to this reactor vessel 9 are at least one burner 10 as fuelsupply means and at least one combustion air supply 11. The combustionair supplies 11 advantageously contain corresponding fans and connectingconduits connected to the circumference of the reactor vessel 9, so thatcombustion air and optionally additional mixed gases can be blownthereby—preferably controllably—into this reactor vessel 9. The burneris preferably adjustably or controllably co-ordinated with the upper endof the reactor vessel 9 so that suitable gaseous, solid and/or liquidfuels can be burnt sub-stoichiometrically in the reactor vessel 9.

Furthermore, it is regarded as particularly advantageous if this reactorvessel 9 is simultaneously constructed as a combustion chamber used inthe aforementioned manner and as a reduction vessel for a first reducingtreatment of the preheated and calcined fine ores (arrow 1). Thereforethe reactor vessel 9 has at least one feed pipe 12 for fine or at itsupper end.

As can also be seen in FIG. 1, in the material conduit 3 a for thepreheated and calcined fine ores which leads from the second, middlecyclone stage 3 to the lowest cyclone stage (reduction heat exchangerstage) 2, there is disposed an adjustable branching or distributingdevice 13, from which a first branch conduit 3 a′ leads to the lower endregion of the uptake conduit section 8 a of the reactor loop 8 and asecond branch conduit 3 a″ leads to the feed pipe 12 of the reactorvessel 9. In this way, in case of need or in adaptation to theparticular desired/necessary degree of reduction, the entire preheatedand calcined fine ores can be introduced either directly into the uptakeconduit section 8 a of the reactor loop 8 or previously into the reactorvessel 9, or adjustable fractions of the preheated and calcined fineores can be introduced partially into the reactor loop 8 (uptake conduitsection 8 a) and partially into the reactor vessel 9.

The fine ores subjected in the reactor vessel 9 to a first partialreduction with the reducing gas produced therein are then introduced viathe connecting or feed conduit 7 together with the still unconsumed hotreducing gases into the lower end region of the uptake conduit section 8a of the reactor loop 8, and are advantageously introduced above theconnection point for the supply of the hot gases (arrows 5) and belowthe feed point for the direct supply of preheated and calcined fine oresinto this reactor loop 8. It will be apparent that the fine oressubjected to a first reduction treatment in the reactor vessel have beenparticularly intensively and thoroughly reduced after passing throughthe reactor loop 8 and the appertaining precipitating cyclone 2 a.

As has already been explained above in the explanation of the methodaccording to the invention, care is taken to ensure that the reducinggas produced contains a sufficient proportion of CO and H₂ gases for thereduction work, i.e. in order to be able to achieve suitable degrees ofreduction, these gases are present in an excess quantity in the risinghot gas stream at least in the lowest cyclone stage 2. They can undergosecondary combustion and can be used for the heating and temperaturecontrol. For this purpose, it may be advantageous if at least one supplyconnection 14 (advantageously with associated fan) for supplying furthercombustion air and/or pure oxygen for the secondary combustion ofreducing gas is connected to the reactor loop 8 and optionally to atleast one rising gas conduit to the upper cyclone stage 3, 4.

Thus this additional combustion air (and/or oxygen) can advantageouslybe blown in as required and adjustably into the reactor loop 8 andoptionally also into at least one gas conduit of the upper cyclonestages 3, 4, so that if necessary secondary heating of the rising hotgas stream can take place in order always to be able to ensure anoptimal heat treatment of the supplied fine ores in the gas suspensionpreheater I.

As has already been mentioned, the reduction heat exchanger stage, i.e.the lowest cyclone stage 2 of the gas suspension preheater I in theexample according to FIG. 1 has an after-treatment kiln III in the formof at least one electric kiln disposed downstream of it. A correctivereduction or a final reduction or secondary reduction of the reducedfine ores leaving the gas suspension preheater I can basically beundertaken in this after-treatment kiln III if this is necessary for apredetermined further treatment of the fine ores.

Depending upon the construction or the mode of operation of the electrickiln, it may be advantageous for the reduced ores coming from the gassuspension preheater I to be introduced directly into the electric kilnor for them to be made lumpy beforehand by briquetting them in the hotstate, for which purpose according to FIG. 1, a hot-briquetting press 15as well as a suitable changeover valve or the like is indicated in theregion between the gas suspension preheater I and the electric kiln.

In the case of the connection of the after-treatment kiln/electric kilnIII downstream as previously described, it may also be necessary foradditional coal, preferably in the form of fine coal, to be supplied tothe hot reduced fine ores coming from the precipitating cyclone 2 a ofthe lowest cyclone stage (reduction heat exchanger stage) 2. Therefore aconduit 17 for the metered supply of fine coal is also connected to thematerial conduit 16 leading from the precipitating cyclone 2 a of thereduction heat exchanger stage/lowest cyclone stage 2 to the electrickiln/after-treatment kiln III. This fine coal to be delivered to thekiln III connected downstream is advantageously comminuted to a grainsize of smaller than 3 mm, preferably smaller than 1 mm.

In connection with the devices disposed downstream of the gas suspensionpreheater I in the ore flow direction (continuous arrows 1), referenceshould also be made at this point to the variant of the apparatusaccording to the invention which is illustrated in FIG. 2. For the sakeof simplicity, of the gas suspension preheater I, this partialrepresentation in FIG. 2 shows only the lowest cyclone stage 2 thereofconstructed as a reduction heat exchanger stage with the reactor loop 8,the reactor vessel 9 and the cyclone precipitator 2 a, which isconnected via its downwardly leading material conduit 16 and optionallyvia a branching device 18 disposed in this material conduit 16 on theone hand directly to a rotary kiln 19 and on the other hand to anindirect rotary cooler 20.

In this variant (FIG. 2), the rotary kiln 19—instead of at least oneelectric kiln—forms the after-treatment kiln III in order to subject thereduced fine ore coming from the gas suspension preheater I or from thelowest cyclone stage 2 thereof to a corrective or final reduction ifthis is necessary. Also in this case, the hot exhaust gases from therotary kiln 19 or the after-treatment kiln III can be introduced via akiln exhaust gas conduit 6′ as hot gases (broken arrows 5) into thereactor loop 8. The finally reduced fine ores discharged from thisrotary kiln 19 can then if required be introduced into the indirectrotary cooler 20 and can be cooled there in a manner which is known perse to an adequate temperature, for example below approximately 120° C.

Basically in special applications, there is also a possibility ofsubjecting the fine ores to a first secondary reduction in the rotarykiln and to a second secondary reduction in a subsequent electric kiln.

Also in the after-treatment of the reduced fine ores coming from thelowest cyclone stage 2 of the gas suspension preheater I, it may beadvantageous to measure in and to mix with them a correspondingly largefraction of fine coal before or as they enter the rotary kiln 19, forwhich purpose a fine coal metering container 21 with a metering conveyor22 can be connected to the lower end of the material conduit 16.Furthermore, it may be advantageous in this connection if fans 23 forsupplying additional combustion are disposed in a manner which is knownper se on the rotary kiln 19, particularly on the shell thereof.

As has already been indicated above, due to the arrangement of thebranching device 18 in the material conduit 16 coming from the gassuspension preheater I, a possibility also exists of bypassing therotary kiln 19, i.e. by excluding or avoiding a corrective or finalreduction and delivering the fine ores (arrow 1) thoroughly reduced inthe lowest cyclone stage 2 directly to the rotary cooler 20. Thesereduced fine ores can then be cooled in the necessary manner—forinstance for a corresponding chemical further treatment.

In the embodiment of the reduction apparatus illustrated in FIG. 1possibilities also exist for preparing the starting ores in a suitablemanner before they are supplied to the gas suspension preheater Idescribed above, i.e. for sufficiently drying damp starting ores andcomminuting starting ores in relatively large lumps in the necessarymanner. For this reason, suitable devices for drying and/or comminutionof damp and/or lumpy starting ores are connected upstream of the gassuspension preheater I, and these devices are supplied with the hotexhaust gases (broken arrows 5 a) from the gas suspension preheater I,i.e. the exhaust gases from the gas suspension preheater I which arestill hot can still be utilized for drying the starting ores and arefurther cooled thereby.

According to the embodiment illustrated in FIG. 1, the devices fordrying and/or comminution of the starting ores can advantageously beformed by the drying and grinding apparatus II already mentioned abovewith the associated pneumatic conveyor dryer 24. This drying andgrinding apparatus II can be constructed in a manner which is known perse and can contain as principal apparatus parts for example any suitablemill (e.g. high-speed pulveriser, tube mill with or without dryingchamber and the like) 25 and at least one air classifier 26, the milland the classifier being connected to one another by a gas conduit orthe pneumatic conveyor dryer 24.

Damp and/or lumpy starting ore (arrow 1 a) from a storage container 27is delivered via a conveyor device 28 and metered to the mill 25, towhich the hot exhaust gases from the heat exchanger (arrows 5 a) arealso delivered via a fan 29, and optionally fresh air (via a feed pipe30) and/or hot air (via a hot air conduit 31) can also be mixed in withthese hot exhaust gases from the heat exchanger (5 a). The starting orescomminuted in the mill 25 and dried in the pneumatic conveyor dryer 24are separated in the air classifier 26 into fines/fine ores and oversizematerial or tailings.

Whilst the tailings—according to arrow 1 c—are returned to the mill 25for further comminution, the sufficiently comminuted fine ores are ledtogether with the exhaust gases into a precipitator 32 where the fineores are separated from the hot exhaust gases. Whilst the separated fineores (arrow 1) are delivered to the gas suspension preheater I, theexhaust gases (broken arrows 5 a) are delivered to a suitable dustcollector 33 in which the ore dust (finest ores) still contained inthese exhaust gases are separated out. This precipitated ore dust (arrow1 b) can either be processed in another way or—as will generally beadvantageous—can be delivered to the ores to be reduced or optionallyalso to the largely finally reduced ores at appropriate points, asindicated in FIG. 1 by suitable conduits and conveyor means.

For this purpose in particular, a pneumatic dust conveyor 34 can beprovided, the conduit of which leads from the dust collector 33 to thegas suspension preheater I, but particularly advantageously it leadspreviously into an intermediate container 35 from which the ore dust ismetered and delivered to the corresponding points in particular in theregion of the lowest cyclone stage 2 of the gas suspension preheater I.In parallel with this, a fine coal bin 36 can also be provided ifrequired, from which—as explained above—a corresponding fraction of finecoal can be metered (e.g. via the conduit 17) into the fine ores stillto be finally reduced in the after-treatment kiln III.

The drying and grinding apparatus II can also be constructed so that thefraction of coal or fine coal necessary for the above-mentionedcorrective or final reduction in the after-treatment kiln III, therotary kiln 19 is comminuted together with the starting ores 1 a in thisdrying and grinding apparatus II.

In the embodiment of the reduction apparatus illustrated in FIG. 1, apossibility also exists—as indicated by corresponding conduit arrows—ofintroducing a fraction of fine coal from the fine coal bin 36—togetherwith ore dust and/or preheated and calcined ores—into the reactor vessel9 if required.

1. A method for reduction of fine ores, in which prepared fine ores passfrom the top downwards through a multi-stage gas suspension preheatergenerally in countercurrent flow to rising hot gases and are preheatedand calcined in at least one upper heat exchanger stage and then aresubjected to a reducing heat treatment in at least one lower heatexchanger stage with a reducing agent being added into the delivered hotgas stream, wherein the principal part of the reducing heat treatment ofthe preheated and calcined fine ores is carried out in a reactor loopspecially constructed in the lowest heat exchanger stage of the gassuspension preheater, said reactor loop has an uptake conduit sectionand a curved section adjoining the uptake conduit section and with whichthe reactor loop opens into at least one precipitating cyclone which isdisposed downstream, and for this purpose a hot gaseous reducing agentis introduced into the rising hot gas stream.
 2. A method as claimed inclaim 1, wherein the hot gaseous reducing agent is produced as areducing gas in a separate reactor vessel associated with the reactorloop by sub-stoichiometric burning of gaseous, liquid and/or solid fuelsand from there is introduced into the reactor loop.
 3. A method asclaimed in claim 2, wherein in addition to the fuels combustion air andmixed gases are introduced into the reactor vessel (9).
 4. A method asclaimed in claim 2, wherein at least some of the preheated and calcinedfine ores are introduced into the reactor vessel which simultaneouslyforms a combustion chamber and a reduction vessel, the said ores beingexposed in this reactor vessel to a first partial reduction by means ofthe reducing gas produced there and thereafter are introduced togetherwith the reducing gas into the reactor loop for further reduction.
 5. Amethod as claimed in claim 1, wherein additional combustion air and/orpure oxygen is introduced at at least one point along the length of thereactor loop and of the upper heat exchanger stage for secondarycombustion of the reducing gas.
 6. A method as claimed in claim 1,wherein the fine ores coming from the reducing heat exchanger stage ofthe gas suspension preheater are subjected to a further correctiveand/or final reduction in a rotary kiln or at least one electric kiln.7. A method as claimed in claim 6, wherein the reduced fine ores comingfrom the lowest heat exchanger stage of the gas suspension preheater orthe fine ores after-treated in the rotary kiln are introduced directlyor in the hot-briquetted state into the electric kiln.
 8. A method asclaimed in claim 6, wherein in order to support the corrective and/orfinal reduction in the rotary and/or electric kiln, fine-grained coaland/or organic materials are added to the fine ores as additionalreducing agent.
 9. A method as claimed in claim 8, wherein the hotexhaust gases containing the reducing gas from the kiln which isdisposed downstream of the gas suspension preheater in the ore flowdirection are introduced as hot gases into the reactor loop.
 10. Amethod as claimed in claim 1, wherein the reduced fine ores are cooledin a cooling zone which is formed by an indirect rotary cooler.
 11. Amethod as claimed in claim 1, wherein for the reduction of damp startingores these ores are dried with the aid of hot exhaust gases from the gassuspension preheater.
 12. A method as claimed in claim 1, wherein atleast partially lumpy and damp starting ores are first of all comminutedand dried before their reduction, this comminution and drying beingcarried out in a drying and grinding apparatus with hot exhaust gasesbeing delivered from the gas suspension preheater.
 13. A method asclaimed in claim 8, wherein together with the starting ores, a fractionof coal for a corrective or final reduction is comminuted in a kilndisposed downstream of the gas suspension preheater.
 14. A method asclaimed in claim 12, wherein dust which accumulates during drying and/orcomminution is precipitated out of the exhaust gas stream and delivereddirectly to the reactor loop of the gas suspension preheater and/or tothe kiln disposed downstream thereof.
 15. A method as claimed in claim8, wherein fine coal comminuted to a grain size of smaller than 3 mm isdelivered to the kiln disposed downstream.
 16. A method as claimed inclaim 1, wherein the reduction work is carried out in the lowest heatexchanger stage of the gas suspension preheater containing the reactorloop at a temperature of approximately 600 to 1000° C.
 17. A method asclaimed in claim 1, wherein reducing gas containing CO and/or H₂ is usedfor the reduction of the preheated and calcined fine ores in the lowestheat exchanger stage.
 18. A method as claimed in claim 1, wherein forthe reduction of damp starting ores, these ores are dried with the aidof hot exhaust gases from the gas suspension preheater in a pneumaticconveyor dryer.
 19. A method as claimed in claim 8, wherein fine coalcomminuted to a grain size of smaller than 1 mm is delivered to the kilndisposed downstream.
 20. A method as claimed in claim 1, wherein thereduction work is carried out in the lowest heat exchanger stage of thegas suspension preheater containing the reactor loop at a temperaturebetween approximately 700 and 900° C.